Electrocardiographic monitoring and telemetry have been in use in the United States for some time for screening and diagnosis of cardiopathy. Electrocardiography provides a graphic registration, commonly known as an EKG, of movements of the heart using electrical signal sensing. In general, electrical leads used to transmit signals from the patient's cardiovascular system are fixed to the skin of the patient individually, at suitable locations, using suction cups and conductive adhesives to provide the necessary electrical connection for reading the heart movements through a patient's skin.
For screening and evaluation, the patient should be ambulatory so that readings can be taken during different degrees of physical exertion to demonstrate the reaction of the heart to differing stresses. A standard type of testing includes electrocardiographic monitoring of a patient during a set of standardized treadmill exercises. It is well recognized that this type of screening and evaluation are important for diagnosis of new ischemic cardiac episodes in the chronically symptomatic cardiac patient as well as the identification of "silent ischemic" periods of myocardial oxygen insufficiency not associated with classic chest pain. These ischemic electrocardiographic changes can be accurately recognized only if a full screen electrocardiogram is performed. The standard full screen electrocardiogram includes readings taken by electrically conductive leads at standard chest positions combined to provide readings.
Periodic electrocardiograms can provide a physician with a cardiographic profile of an individual patient for early detection and diagnosis of cardiovascular diseases. For purposes of providing an accurate profile, it is important that each electrocardiogram be taken with leads affixed about the same location on the patient. The accuracy of each electrocardiogram requires that the leads be accurately placed and that they remain fixed while the patient is ambulatory. In addition, to provide accurate information for an individual patient, a series of electrocardiograms are taken and compared to one another to detect changes in the reaction of the individual patient's heart to the same stresses. Therefore, it is important that placement of the leads be consistent from one electrocardiogram session to another.
As can be appreciated, accurately placing and securing a large number of leads can be difficult and time consuming. In addition, electrocardiograms are taken periodically and the results compared to one another to provide a continuing profile of an individual patient's heart movements for early diagnosis and treatment of heart disease and to identify "silent ischemic" periods of myocardial oxygen insufficiency in chronically symptomatic cardiac patients. It would therefore be advantageous to have a device for accurate placement of leads for accurately reproducing test conditions for comparison between testing episodes.
Although a full screen, twelve point electrocardiogram provides the most accurate picture for recognizing ischemic electrocardiographic changes, because of the time required to place and secure individual leads, electrocardiograms taken during an acute symptomatic episode of a cardiac patient are generally limited to two- to four-lead readings. It would therefore be advantageous to have a device which enables more leads to be accurately placed and secured quickly during an acute symptomatic episode.
U.S. Pat. No. 4,608,987 to H. E. Mills relates to a vest-like garment having a plurality of aperatures adapted for receiving electrodes. However, there is no provision to ensure that the electrodes are placed each time of reuse of the vest about the same location.
U.S. Pat. No. 4,583,549 to S. Manoli relates to an ECG electrode pad with a plurality of ECG electrodes which are repositioned with regard to each other and not with reference to their previous position.
U.S. Pat. No. 4,365,634 to Bare et al discloses a multiterminal electrode construction having a pair of separate support members adapted for the transcutaneous application of an electrode to a patient. A multiterminal design is provided by a conductive pattern printed on a semiflexible sheet. The pattern is printed with conductive ink in a binder composition. However, there is no means provided which can ensure the reapplication of the terminals to the same location so as to obtain a better comparison of test results.
U.S. Pat. No. 4,593,698 to R. J. Athans discloses an electrocardiograph sensor positioning device for repeatedly positioning electrocardiograph sensors. The device establishes a longitudinal reference between two anatomical landmarks on an individual. A second reference path is then found and recorded. The recorded locations are necessary to ensure a similar location. One of the problems with the use of the device requires that the second examining physician have the information from the first physician in order to obtain readings at the same locations. The device of the invention provides uniform examination without requiring information from others on placement of the electrodes.
U.S Pat. No. 4,763,660 discloses a multilayer disposable electrode belt device which contains a plurality of flexible non-conductive layers. There is also provided anatomatical placement reference means.
Telephonic units for transmitting ECG signals to ECG receiving equipment at a cardiologist's office are described generally in U.S. Pat. No. 3,910,260. Usually such transmission takes place in emergency vehicles where prior medical history may not be readily available. In order to obtain meaningful and reliable information repeatable ECG signals are necessary for the cardiologist. None of the prior art devices have provided a low cost solution to obtaining repeatable ECG signals in the field by untrained or non-professionals parties.
The present invention provides an easily manufactured accurate, repeatable placement of leads for electrocardiograms which is repeatable without knowledge of the previous locations. The device of this invention lowers the time involved in placement and affixation by providing a sensor sheet incorporating multiple leads which are preferably pre-wired to a terminus that can connect to a standard electrocardiographic cable or to a telemetric unit, as more fully discussed below.